A so-called wash-out type toilet that washes away waste due to an action of running water that is provided by a drop of water has conventionally been known as one kind of flush toilet (see, for example, Japanese Laid-open Patent Publication No. 2016-176320). A waste discharge performance of a wash-out type toilet is determined by, for example, a water level difference of retained water in a bowl that is caused at a time of toilet washing.
That is, a waste discharge performance is determined depending on a water level difference between a water level of retained water before a start of washing and a highest water level of retained water at a time when washing water is supplied after the start of washing, and for example, such a discharge performance is improved with increasing such a water level difference.
However, water saving is desired for a flush toilet in recent years and an amount of washing water that is supplied to a bowl is reduced. As an amount of washing water is reduced, it may be impossible to ensure a water level difference as described above sufficiently and a discharge performance may be degraded. Thus, there is room for improvement in a wash-out type toilet according to a conventional technique in that a waste discharge performance thereof is improved.